This craft is 20 feet long and 8 feet wide, with a draft of 2 feet, and is identical to a river boat (and can be used as one). As it is magical, however, its Armor'Class is 4 and has 40 Hull Points. No rowers or sailors are needed if the command words are known. The command words for the undersea boat are simple anagrams:

Command Command Word
Start Ratts
Stop Opts
Turn to port Runt potrot
To starboard Burnt toast odarr
Stop turning Piston grunt
Submerge Rubes gem
Level off Elf ov elf
Surface Fur aces

When underwater, the boat radiates a water breathing effect, protecting all passengers and crew as long as they touch the boat and it is fitted with grips so passengers won't drift away.